My husband and I are traveling (on I95) with our 3 yr old and 21 month old (yikes) rom...

My husband and I are traveling (on I95) with our 3 yr old and 21 month old (yikes) rom east GA to upstate Ny to pick up my 8 yr old stepdaughter for the summer. We hoped to stop at cheap/free places for a break on the way back. Any suggestions on places for little kids to see/do/run?

Washington, D.C., might be a good option on the way home? Lots of things for kids to do, much of it free! Here's a blog post about 50+ free activities in D.C.: http://blogs.away.com/travel/2009/01/dc-for-free-50.html. Another great thing about the city is that there's loads, including parks and a zoo, where kids can roam free.